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#High-speed lasers create images that respond to strokes without burning the skin By Victoria Woollaston for Mailonline Published: 13:53 GMT, 29 june 2015 Updated: 23:40 GMT, 29 june 2015 From Princess Leia in Star wars to a holographic Tupac at the 2013 Coachella festival, holograms have fascinated scientists for decades. But because they use lasers to project the hologram, it makes interacting with the images potentially dangerous-until now. Researchers have created 3d holograms using lasers that fire at a quadrillionth a second, and they respond to touch without burning the user's skin. Scroll down for video Researchers from the University of Tokyo used femtosecond lasers to create 3d holograms that are safe to touch and respond in real time. A femtosecond is a quadrillionth of a second and these pulses ionise the air to create plasma which can be touched (pictured) The breakthrough was made by Japanese researchers from the University of Tokyo, University of Tsukuba, Utsunomiya University Nagoya Institute of technology. Holography uses lasers to record the brightness, contrast and dimensions of an image and project this image, typically in 3d, which can be viewed without specialist glasses. When pixels are beamed and visible in 3d space they're known as voxels and are created when the energy from the laser ionises the air and releases extra energy in the form of photons which glow purple and blue. Researchers and companies have used this technology to create plasma displays in the past but these involved lasers that pulse with bursts that last for nanoseconds, for example. Although this is a relatively short period of time, it is long enough for the bursts to be able to damage the skin or the surface of a material if touched. To solve this problem the Japanese researchers created plasma voxels using femtosecond lasers instead. A femtosecond is a quadrillionth of a second and these lasers pulse with bursts that last between 30 and 270 femtoseconds at a time. The researchers fired the femtosecond laser through what's known as a spatial light modulator and a series of lenses into a Galvano scanner. This scanner positions the beam through two more lenses onto a mirror to finally show the final voxel shape, dubbed Fairy Lights. A camera under the hologram is then able to capture and record a user's interactions, allowing the voxels to be touched.''In reality, when a person touches the voxels the finger generates a shockwave, which the user feels as an pulse. And because of the high-speed nature of the femtoseconds, the voxels are able to respond in real-time to these touches. In a video revealing the technology, the touches are shown being used to tick a virtual checkbox, to change the word'hate'to'love 'and to switch between an image of a heart and a broken heart. An illustration in the research paper, called Fairy Lights in Femtoseconds: Aerial and Volumetric Graphics Rendered by Focused Femtosecond Laser Combined with Computational Holographic Fields, additionally shows it being wrapped around objects and used to create a virtual plant.''We present a method of rendering aerial and volumetric graphics using femtosecond lasers, 'explained the team. In a video revealing the technology, the touches are shown being used to tick a virtual checkbox (pictured), to change the word'hate'to'love 'and to switch between an image of a heart and a broken heart'A high-intensity laser excites a physical matter to emit light at an arbitrary 3d position.''Popular applications can then be explored especially since plasma induced by a femtosecond laser is safer than that generated by a nanosecond laser.''The holograms and workspace of the system are up to 1cm3 in volume but the researchers said they could be scaled up depending on what the technology is needed for i

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